Toothform for a cutting tool, such as a hole saw

ABSTRACT

A cutting tool includes a generally cylindrical body, a plurality of cutting teeth formed on the generally cylindrical body, a plurality of non-cutting protrusions formed on the generally cylindrical body, and a plurality of gullets formed on the generally cylindrical body. Each gullet is formed between one of the plurality of cutting teeth and one of the plurality of non-cutting protrusions. Each gullet has a base and a gullet depth measured from the base to a tip of a corresponding cutting tooth. Each non-cutting protrusion is located approximately halfway between the tips of two adjacent cutting teeth and has a height that is at most about 75% of the gullet depth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/673,131, filed Jul. 18, 2012 by Jason Thom et al. and titled“TOOTHFORM FOR A CUTTING TOOL, SUCH AS A HOLE SAW,” the entire contentsof which are incorporated by reference herein.

BACKGROUND

The present invention relates to toothforms for cutting tools and, moreparticularly, to toothforms for hole saws.

Hole saws are typically used to cut holes in work pieces made of wood ormetal. During use, cutting teeth of the hole saws may be impacted bynails or other hard objects embedded in the work pieces.

SUMMARY

In one embodiment, the invention provides a cutting tool including agenerally cylindrical body having an open end and a closed end, and aplurality of cutting teeth formed on the open end of the generallycylindrical body. Each cutting tooth includes a tip, a rake faceextending from the tip, and a relief surface extending from the tip. Thecutting tool also includes a plurality of non-cutting protrusions formedon the open end of the generally cylindrical body. Each non-cuttingprotrusion has an apex. The cutting tool further includes a plurality ofgullets formed on the open end of the generally cylindrical body. Eachgullet is formed between one of the plurality of cutting teeth and oneof the plurality of non-cutting protrusions. Each gullet has a base anda gullet depth measured from the base to the tip of a correspondingcutting tooth. Each non-cutting protrusion is located approximatelyhalfway between the tips of two adjacent cutting teeth. Each non-cuttingprotrusion has a height measured from the base of the gullet to the apexthat is at most about 75% of the gullet depth.

In another embodiment, the invention provides a cutting tool including agenerally cylindrical body having an open end and a closed end, and aplurality of cutting teeth formed on the open end of the generallycylindrical body. Each cutting tooth includes a tip, a rake faceextending from the tip, a planar relief portion extending from the tip,a concave relief portion extending from the planar relief portion, and aconvex relief portion extending from the concave relief portion. Thecutting tool also includes a plurality of gullets formed on the open endof the generally cylindrical body. Each gullet is formed between therake face of one cutting tooth and the convex relief face portion of anadjacent cutting tooth. Each cutting tooth has a tooth width measuredfrom the rake face through the convex relief portion. The concave reliefportion of each cutting tooth forms at least about 40% of the toothwidth.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a hole saw including a toothformaccording to one embodiment of the invention.

FIG. 2 is a side view of the hole saw shown in FIG. 1, the hole sawbeing illustrated in a flattened condition.

FIG. 3 is an edge view of the hole saw shown in FIG. 2.

FIG. 4 is an enlarged view of a portion of the hole saw shown in FIG. 2.

FIG. 5 is a perspective view of a hole saw including a toothformaccording to another embodiment of the invention.

FIG. 6 is a side view of the hole saw shown in FIG. 5, the hole sawbeing illustrated in a flattened condition.

FIG. 7 is an edge view of the hole saw shown in FIG. 5.

FIG. 8 is an enlarged view of a portion of the hole saw shown in FIG. 6.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. As used herein, the term “about”means within one significant figure when referring to a length,distance, angle, slope, or the like, and within one percent whenreferring to a percentage.

DETAILED DESCRIPTION

FIG. 1 illustrates a cutting tool 10 embodying the invention. In theillustrated embodiment, the cutting tool 10 is a hole saw. The hole saw10 is connectable to and driven (e.g., rotated) by a power tool, such asa drill, to cut holes and/or remove plugs from a work piece.

The illustrated hole saw 10 includes a generally cylindrical body 14having a first, closed end 18 and a second, open end 22. The first end18 is configured to mount to an arbor for connecting the hole saw 10 toa chuck of a power tool. The second end 22 includes a toothform 26 thatis configured to cut through a work piece. At least one opening 30 isformed in the body 14 between the first and second ends 18, 22 tofacilitate chip and plug removal from the hole saw 10.

As shown in FIG. 2, the toothform 26 is defined by cutting teeth 34,non-cutting protrusions 38, primary gullets 42, and secondary gullets46. The teeth 34 are all generally the same shape and size. Oneprotrusion 38 is associated with each tooth 34 and positioned forward ofthe tooth 34 in a cutting direction such that the teeth 34 and theprotrusions 38 are paired together. The primary gullets 42 are formedbetween pairs of adjacent teeth 34 and protrusions 38. One of thesecondary gullets 46 is formed between the tooth 34 and the protrusion38 in each pair. This pattern of tooth 34, secondary gullet 46,protrusion 38, and primary gullet 42 repeats along the entire length ofthe second end 22 of the body 14 to define the toothform 26. In theillustrated embodiment, the teeth 34 are spaced apart such that thetoothform 26 has a pitch P₁ of between about 0.2 inches and about 0.5inches. In other embodiments, the teeth 34 may be spaced apart by alarger or smaller amount.

As shown in FIG. 3, the hole saw body 14 has a thickness T₁ of about0.05 inches. In other embodiments, the body 14 may be relatively thinneror thicker. The body 14 is bent into a circle and welded together at aweld line 50 (FIG. 1) to form the generally cylindrical shape of thehole saw 10.

FIG. 4 illustrates one pair of a tooth 34 and a protrusion 38, with asecondary gullet 46 positioned therebetween, in more detail. Theillustrated tooth 34 includes a rake face 54, a tip 58, a primary reliefsurface 62, and a secondary relief surface 66. The tip 58 defines acutting plane 70 that is generally parallel to the second end 22 of thebody 14. The tooth 34 has a first height H₁ measured from a base of thecorresponding secondary gullet 46 to the tip 58 of the tooth 34, and asecond height H₂ (FIG. 2) measured from a base of the correspondingprimary gullet 42 to the tip 58 of the tooth 34. In the illustratedembodiment, the first height H₁ is between about 0.02 inches and about0.11 inches, and the second height H₂ is between about 0.05 inches andabout 0.12 inches.

The primary relief surface 62 extends from the tip 58 and is angledrelative to the cutting plane 70 by a primary relief angle A₁. In theillustrated embodiment, the primary relief angle A₁ is between about 10degrees and about 40 degrees. In addition, the primary relief surface 62has a relief length L₁ measured from the tip 58 to the secondary reliefsurface 66 of between about 0.02 inches and 0.1 inches.

The secondary relief surface 66 extends from the primary relief surface62 and transitions into the primary gullet 42. The secondary reliefsurface 66 is angled relative to the cutting plane 70 by a secondaryrelief angle A₂ that is greater than the primary relief angle A₁. In theillustrated embodiment, the secondary relief angle A₂ is between about30 degrees and about 70 degrees.

The rake face 54 extends from the tip 58 and transitions into thesecondary gullet 46. The rake face 54 is angled relative to the cuttingplane 70 by an angle A₃. In the illustrated embodiment, the angle A₃ isbetween about 45 degrees and about 90 degrees such that the tooth 34 hasa rake angle of between about 0 degrees and about 45 degrees and anincluded angle between about 5 degrees and about 80 degrees. In someembodiments, the rake angle may be about 25 degrees and the includedangle may be about 45 degrees. In other embodiments, one or moredimensions of the tooth 34 (such as the first height H₁, the secondheight H₂, the primary relief angle A₁, the relief length L₁, thesecondary relief angle A₂, or the rake angle) may be relatively largeror smaller.

The non-cutting protrusion 38 is a generally rounded projection formedin the second end 22 of the body 14 in front of the rake face 54 of thetooth 34. The protrusion 38 helps protect the tooth 34 from majorimpacts and helps guide material while the hole saw 10 cuts through awork piece. In particular, the protrusion 38 limits the amount of thetooth 34 that is exposed during cutting operations to only the portionof the tooth 34 that actually cuts the work piece (e.g., the tip 58 ofthe tooth 34). Such an arrangement reduces the amount of material thatmay enter the gullet 46 in front of the tooth 34.

The illustrated protrusion 38 includes an apex 74, which represents thehighest point of the protrusion 38, a leading edge 78, and a trailingedge 82. The protrusion 38 is generally shorter than the correspondingtooth 34 such that the apex 74 is spaced apart a first distance D₁ fromthe cutting plane 70. In addition, the apex 74 is spaced apart a seconddistance D₂, measured parallel to the cutting plane 70, from the tip 58of the tooth 34. In the illustrated embodiment, the first distance D₁ isbetween about 0.01 inches and about 0.02 inches, and the second distanceD₂ is between about 0.1 inches and about 0.15 inches. In otherembodiments, the first and second distances D₁, D₂ may be larger orsmaller.

The leading edge 78 extends from the apex 74 to the primary gullet 42.The trailing edge 82 extends from the apex 74 to the secondary gullet46. In the illustrated embodiment, the leading and trailing edges 42, 46are curved such that the protrusion 38 has a radius R₁ of between about0.02 inches and about 0.07 inches. In other embodiments, the protrusion38 may form a larger or smaller radius. In still other embodiments, theleading and/or trailing edges 42, 46 may have different geometries, suchas linear edges.

As shown in FIG. 2, each of the primary gullets 42 forms a trough areabetween adjacent pairs of teeth 34 and protrusions 38. The illustratedprimary gullets 42 define radii R₂ of between about 0.1 inches and about0.2 inches. In other embodiments, the primary gullets 42 may definelarger or smaller radii.

Referring back to FIG. 4, the secondary gullet 46 is formed in thesecond end 22 of the body 14 between the tooth 34 and the protrusion 38in a given pair. Each of the secondary gullets 46 is generally shallowerthan the primary gullets 42. In the illustrated embodiment, thesecondary gullet 46 has a radius R₃ of between about 0.03 inches andabout 0.06 inches. In other embodiments, the secondary gullet 46 mayhave a larger or smaller radius.

FIG. 5 illustrates another cutting tool 110 embodying the invention.Similar to the cutting tool 10 discussed above, the illustrated cuttingtool 110 is a hole saw. The hole saw 110 of FIG. 5 includes similarfeatures as the hole saw 10 of FIG. 1. In particular, the illustratedhole saw 110 includes a generally cylindrical body 114 having a first,closed end 118, a second, open end 122, and at least one opening 126formed in the body 114 between the ends 118, 122 to facilitate chip andplug removal.

The hole saw 110 also includes a toothform 130 formed on the open end122 of the body 114. As shown in FIG. 6, the toothform 130 is defined bya repeating pattern of cutting teeth 134, non-cutting protrusions 138,and gullets 142. The illustrated teeth 134 have generally the sameshape, but vary in size around the open end 122 of the body 114. In theillustrated embodiment, the toothform 130 includes a pattern of fivecutting teeth 134 that repeats around the open end 122 of the body 114,giving the hole saw 110 a 4/6 tooth per inch (TPI) pitch. In otherembodiments, the toothform 130 may include a pattern of fewer or morecutting teeth 134 that repeats around the open end 122 of the body 114.In still further embodiments, each of the cutting teeth 134 may begenerally the same size. Additionally or alternatively, the pitch of thecutting teeth 134 may be constant.

Each gullet 142 is formed between one of the teeth 134 and one of theprotrusions 138 so that a pattern of tooth 134, gullet 142, andprotrusion 138 repeats along the entire length of the open end 122 ofthe body 110. In addition, each protrusion 138 is positioned closeenough to a successive cutting tooth 134 that the protrusion 138 and thecutting tooth 134 are merged together into a single cutting body.Together, the cutting tooth 134 and the protrusion 138 define a toothwidth W₁.

As shown in FIG. 7, the hole saw body 114 has a thickness T₂ of about0.05 inches. In other embodiments, the body 114 may be relativelythinner or thicker.

FIG. 8 illustrates a portion of the toothform 130 in more detail. Theillustrated tooth 134 of the toothform 130 includes a tip 146, a rakeface 150 extending in a first direction from the tip 146, and a reliefsurface 154 extending in a second direction from the tip 146. The tip146 defines a cutting plane 158 that is generally parallel to the closedend 118 of the body 114. The tooth 134 has a tooth height H₃ measuredfrom a base 162 of the gullet 142 positioned forward of the tooth 134 inthe cutting direction to the cutting plane 158 defined by the tip 146 ofthe tooth 134. The tooth height H₃ also represents a gullet depth of thegullet 142. In the illustrated embodiment, the tips 146 of the cuttingteeth 134 all define the same cutting plane 158. The cutting teeth 134have different heights, which is achieved by varying the sizes (i.e.,depths) of the corresponding gullets 142 (e.g., by varying the locationsof the bases 162 of the gullets 142 relative to the closed end 118 ofthe body 114). In other embodiments, the tips 146 of the cutting teeth134 may define different cutting planes.

The rake face 150 of the tooth 134 extends from the tip 146 andtransitions into the gullet 142. The illustrated rake face 150 has arelatively large positive rake angle A₄, but is relatively short. In theillustrated embodiment, the rake angle A₄ is about 7 degrees (measuredfrom a plane perpendicular to the cutting plane 158). In addition, alength L₂ of the rake face 150 is between about 0.006 inches and about0.012 inches. In other embodiments, the rake angle A₄ may be relativelylarger, smaller, or even negative, and/or the rake length L₂ may berelatively longer or shorter.

The illustrated relief surface 154 of the tooth 134 includes a planarrelief portion 166 and a concave relief portion 170. The planar reliefportion 166 extends from the tip 146 to the concave relief portion 170.The concave relief portion 170 extends from the planar relief portion166 to the protrusion 138. The concave relief portion 170 is concavetoward the closed end 118 of the body 114 to form a secondary gullet 172between the tip 146 of the cutting tooth 134 and the protrusion 138. Asshown in FIG. 8, each of the cutting teeth 134 is divided into a firstportion 134A and a second portion 134B by a weld line 174. In theillustrated embodiment, the concave relief portion 170, and thereby thesecondary gullet 172, is positioned one side of the weld line 174 (e.g.,above as shown in FIG. 8) such that the weld line 174 of each tooth 134is not interrupted by the secondary gullet 172.

Since the non-cutting protrusion 138 is merged with the cutting tooth134, the protrusion 138 extends from an end of the relief surface 154opposite from the tip 146 to form part of the relief surface 154. Inparticular, the protrusion 138 forms a convex relief portion of therelief surface 154 that extends from the concave relief portion 170 andtransitions into the gullet 142. The protrusion 138 is curved in anopposite direction than the concave relief portion 170 (i.e., away fromthe closed end 118 of the body 114) so that the protrusion 138 includesan apex 178 at its furthest point from the closed end 118 of the body114. In the illustrated embodiment, the protrusion 138 is continuouslyrounded and has a radius R₄ between about 0.01 inches and about 0.02inches. In some embodiments, each of the protrusions 138 may havegenerally the same radius of curvature. In other embodiments, each ofthe protrusions 138 in the repeating pattern of the toothform 130 mayhave a different radius of curvature. In further embodiments, theprotrusions 138 may be non-rounded and may come to a point.

Similar to the cutting tooth 134, the non-cutting protrusion 138 has aheight H₄ measured from the base 162 of the adjacent, preceding gullet142 to the apex 178 of the protrusion 138. The height H₄ of theprotrusion 138 is at most about 75% of the gullet depth (or tooth heightH₃) of the corresponding gullet 142. In some embodiments, the height H₄of the protrusion 138 is between about 55% and about 75% of the gulletdepth. In the illustrated embodiment, the height H₄ of the protrusion138 is about 75% of the gullet depth.

As noted above, the cutting tooth 134 and the protrusion 138 togetherdefine the tooth width W₁, which is measured from the rake face 150 ofthe cutting tooth 134 through the protrusion 138 (i.e., to the start ofthe preceding gullet 142). In the illustrated embodiment, the toothwidth W₁ of each tooth 134 is approximately half of a pitch distance P₂from the tip 146 of the tooth 134 to the tip 146 of a preceding tooth134 in the cutting direction of the hole saw 110. In other words, thetooth width W₁ of each tooth 134 is generally equal to a gullet width W₂of the preceding gullet 142, which is measured from the tip 146 of thepreceding tooth 134 to the protrusion 138. With such an arrangement,each non-cutting protrusion 138 is located approximately halfway betweenthe tips 146 of two adjacent cutting teeth 134. By “approximatelyhalfway,” the protrusions 138 may be located at a position between about50% and about 60% of the pitch distance P₂, and preferably at about 50%of the pitch distance P₂.

The illustrated concave relief portion 170 of the relief surface 154extends through a substantial portion of the tooth width W₁ of eachcutting tooth 134, while the planar relief portion 166 of the reliefsurface 154 extends through a relatively small portion of the toothwidth W₁ of each cutting tooth 134. In particular, the concave reliefportion 170 has a length L₃ that forms at least about 40% of the toothwidth W₁, and the planar relief portion 166 has a length L₄ that formsat most about 35% of the tooth width W₁. In some embodiments, theconcave relief portion 170 forms between about 40% and about 75% of thetooth width W₁, and the planar relief portion 166 forms between about15% and about 35% of the tooth width W₁. In the illustrated embodiment,the concave relief portion 170 forms between about 60% and 75% of thetooth width W₁. By forming such a large portion of the tooth width W₁,the concave relief portion 170 defines a more pronounced secondarygullet 172 between the tip 146 of the cutting tooth 134 and thenon-cutting protrusion 138 than if the concave relief portion 170 wassimply a small radius that transitioned from the relief surface 154 ofthe tooth 134 to the protrusion 138. The concave relief portion 170, orsecondary gullet 172, thereby increases the open volume behind the tip146 of the cutting tooth 134 (in the cutting direction), which helpsdefine the shape of the protrusion 138 and helps with chip removal outof the hole saw body 114.

The illustrated gullets 142 are generally non-symmetrical. Each gullet142 is relatively steep and has a large radius R₅ adjacent thecorresponding cutting tooth 134, but is less steep and has a smallerradius R₆ adjacent the non-cutting protrusion 138. In the illustratedembodiment, the gullet 142 transitions from the high positive rake angleA₄ (e.g., 7 degrees) of the rake face 150 to the base 162 of the gullet142 with a relatively steep conic arc, and transitions from theprotrusion 138 to the base 162 of the gullet 142 with a relativelyshallow conic arc. In the illustrated embodiment, the conic arc extendsfrom the protrusion 138, or convex relief portion of the relief surface154, at an initial slope A₅ of about 17 degrees (measured from a planeperpendicular to the cutting plane 158). This more gradual slope A₅helps with manufacturing the transition between the concave shape of thegullet 142 and the convex shape of the protrusion 138. In otherembodiments, the initial slope A₅ of the gullet 142 may be relativelylarger or smaller.

The non-cutting protrusion 138 is positioned forward in the cuttingdirection of the associated tooth 134 to help protect the tooth 134 frombeing sheared off or otherwise damaged during cutting operations.Merging the non-cutting protrusion 138 with the successive cutting tooth134 increases the total width and cross-sectional area of that tooth134, thereby increasing the strength of the tooth 134. In addition,positioning the protrusions 138 relatively close to their successiveteeth 134 helps maintain relatively large gullets 142 between the teeth134 for chip removal during cutting. Such an arrangement allows forfaster cutting speeds using a more aggressive rake angle on each tooth134 and larger pitch distances between the teeth 134 (i.e., smallerTPI), without increasing the possibility of the hole saw 110 bouncingalong or snagging on a work piece.

Although the toothforms 26, 130 have been described above with referenceto a hole saw, the toothforms 26, 130 may also be used on other types ofcutting tools with linear or non-linear cutting edges. For example, insome embodiments, the toothforms 26, 130 may be formed on areciprocating saw blade, a jigsaw blade, a bandsaw blade, a circular sawblade, or the like.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described. Various features and advantages of the invention are setforth in the following claims.

1. A cutting tool comprising: a generally cylindrical body having anopen end and a closed end; a plurality of cutting teeth formed on theopen end of the generally cylindrical body, each cutting tooth includinga tip, a rake face extending from the tip, and a relief surfaceextending from the tip; a plurality of non-cutting protrusions formed onthe open end of the generally cylindrical body, each non-cuttingprotrusion having an apex; and a plurality of gullets formed on the openend of the generally cylindrical body, each gullet being formed betweenone of the plurality of cutting teeth and one of the plurality ofnon-cutting protrusions, each gullet having a base and a gullet depthmeasured from the base to the tip of a corresponding cutting tooth;wherein each non-cutting protrusion is located approximately halfwaybetween the tips of two adjacent cutting teeth, and wherein eachnon-cutting protrusion has a height measured from the base of the gulletto the apex that is at most about 75% of the gullet depth.
 2. Thecutting tool of claim 1, wherein the height of each non-cuttingprotrusion is between about 55% and about 75% of the gullet depth. 3.The cutting tool of claim 1, wherein the height of each non-cuttingprotrusion is about 75% of the gullet depth.
 4. The cutting tool ofclaim 1, wherein one of the plurality of non-cutting protrusions extendsfrom an end of the relief surface of each cutting tooth opposite fromthe tip.
 5. The cutting tool of claim 4, wherein the relief surface ofeach cutting tooth includes a planar relief portion extending from thetip and a concave relief portion extending from the planar reliefportion to the one of the plurality of non-cutting protrusions.
 6. Thecutting tool of claim 5, wherein each cutting tooth has a tooth widthmeasured from the tip through the one of the plurality of non-cuttingprotrusions, and wherein the concave relief portion of each cuttingtooth forms at least about 40% of the tooth width.
 7. The cutting toolof claim 6, wherein the concave relief portion of each cutting toothforms between about 40% and about 75% of the tooth width.
 8. The cuttingtool of claim 6, wherein the planar relief portion of each cutting toothforms at most about 35% of the tooth width.
 9. The cutting tool of claim5, wherein each cutting tooth includes a first portion and a secondportion connected together along a weld line, wherein the concave reliefportion of each cutting tooth forms a secondary gullet between the tipand the one of the plurality of non-cutting protrusions, and wherein thesecondary gullet is positioned on one side of the weld line.
 10. Thecutting tool of claim 4, wherein each cutting tooth has a tooth widthmeasured from the tip through the one of the plurality of non-cuttingprotrusions, wherein each gullet has a gullet width measured from theone of the plurality of cutting teeth to the one of the plurality ofnon-cutting protrusions, and wherein the tooth width is generally equalto the gullet width.
 11. The cutting tool of claim 1, wherein the rakeface of each cutting tooth extends from the tip at a positive rake angleof about 7 degrees.
 12. The cutting tool of claim 11, wherein eachgullet extends from a corresponding non-cutting protrusion at an initialslope of about 17 degrees.
 13. A cutting tool comprising: a generallycylindrical body having an open end and a closed end; a plurality ofcutting teeth formed on the open end of the generally cylindrical body,each cutting tooth including a tip, a rake face extending from the tip,a planar relief portion extending from the tip, a concave relief portionextending from the planar relief face portion, and a convex reliefportion extending from the concave relief portion; and a plurality ofgullets formed on the open end of the generally cylindrical body, eachgullet being formed between the rake face of one cutting tooth and theconvex relief portion of an adjacent cutting tooth; wherein each cuttingtooth has a tooth width measured from the rake face through the convexrelief portion, and wherein the concave relief portion of each cuttingtooth forms at least about 40% of the tooth width.
 14. The cutting toolof claim 13, wherein the concave relief portion of each cutting toothforms between about 40% and about 75% of the tooth width.
 15. Thecutting tool of claim 14, wherein the concave relief portion of eachcutting tooth forms between about 60% and about 75% of the tooth width.16. The cutting tool of claim 13, wherein the planar relief portion ofeach cutting tooth forms at most about 35% of the tooth width.
 17. Thecutting tool of claim 16, wherein the planar relief portion of eachcutting tooth forms between about 15% and about 35% of the tooth width.18. The cutting tool of claim 13, wherein each cutting tooth includes afirst portion and a second portion connected together along a weld line,wherein the concave relief portion of each cutting tooth forms asecondary gullet between the tip and the convex relief portion, andwherein the secondary gullet is positioned on one side of the weld line.19. The cutting tool of claim 13, wherein each gullet has a gullet widthmeasured from the rake face of the one cutting tooth to the convexrelief portion of the adjacent cutting tooth, and wherein the toothwidth is generally equal to the gullet width.
 20. The cutting tool ofclaim 13, wherein the rake face of each cutting tooth extends from thetip at a positive rake angle of about 7 degrees, and wherein each gulletextends from the convex relief portion of the adjacent cutting tooth atan initial slope of about 17 degrees.